Objective: To investigate the main types of the blunt trauma of temporomandibular joint (TMJ) induced by mandible impact and to discuss the concept of TMJ traumatic arthritis. Materials and Methods: The radiograph and clinical data of 41 cases with TMJ traumatic arthritis but without condylar fractures was investigated. Results: 70% of the impact sites were mentums and/or mandible angles; all the cases in the present study could be classified as disk disorders, synovitis, myositis of jaw muscle, adhesion, and mixed pathological changes. Conclusion: TMJ blunt trauma is mainly induced by impact at mandible mentum and angle. TMJ traumatic arthritis induced by blunt trauma is mainly mixed pathological changes and a period of one month is suggested as the boundary for acute and chronic traumatic arthritis.